Remove default email themes (forever)

Is there a way to remove the default email themes (and not have them back in again after each plugin upgrade)?

I have a custom theme for the newsletter, and the (not so computer savvy) users always get confused after an upgrade. I delete them from the themes folder and of course they reappear.

If it is not possible it would be good to have an option to not re-install them after upgrade, or maybe they should install separately after clicking a button from the settings.

https://ww.wp.xz.cn/plugins/newsletter/